Electronic devices each equipped with a light-transmitting touch panel mounted in front of a display element, such as an LCD, have recently grown in number as the devices have covered a broad spectrum and have become multifunctional. Each of the devices is operated by visually identifying and selecting characters, marks, or patterns displayed on the display element through the touch panel, and operating the touch panel.
A conventional touch panel is described with reference to FIGS. 6 to 8.
FIG. 6 is a section of the conventional touch panel. Touch panel 8 includes transparent upper substrate 1, such as a film of polyethylene terephthalate, lower substrate 2 made of glass, transparent resin or the like, light-transmitting upper electrode layer 1A formed on a bottom of upper substrate 1, and light-transmitting lower electrode layer 2A formed on a top of lower substrate 2. Electrode layers 1A, 2A may be made of indium tin oxide (ITO). On the top of lower electrode layer 2A, plural dot spacers 3 made of epoxy, silicon, or the like is formed by printing, provides upper and lower electrode layers 1A and 2A with an established spacing between the layers to face each other. Over the top of lower substrate 2, insulating layer 4 and adhesive layer 5 are formed along an outer border of substrate 2, and upper and lower substrates 1 and 2 are put together by adhesive layer 5. Lower substrate 2 is bonded with adhesive layer 7 to a top of transparent supporter 6 made of resin or the like.
When a top of upper substrate 1 is pressed with a finger or pen, as shown in FIG. 7, upper substrate 1 bends, upper electrode layer 1A contacts with lower electrode layer 2A of lower substrate 2. Consequently, upper electrode layer 1A is electrically connected to lower electrode layer 2A. When a pressing force is released, elastic restoring force of upper substrate 1 makes panel 8 return to that illustrated by FIG. 6.
As shown in FIG. 8, touch panel 8 is installed at a bottom of opening 10A in case 10 of the electronic device, and is mounted to case 10 with holder 12 together with display element 11 (e.g., LCD) disposed below panel 8.
Trough transparent touch panel 8, the characters, the marks, or the patterns displayed on display element 11 are visually identified and selected through pressing upper substrate 1 over element 11. The pressing makes touch panel 8 electrically connected and disconnected. In this way, for example, the electronic device switches among functions, or display element 11 switches among displays.
Since being flat, conventional touch panel 8 mounted to case 10 of the electronic device has a top surface (operating surface) of upper substrate 1 positioned back to a surface of case 10. Therefore, as shown in FIG. 8, the finger or pen touches the surface of case 10 about an outer region of opening 10A when an outer border of upper substrate 1 is pressed for operation. Particularly for this case, a user hardly operate the panel and thus results in improper operation.